This invention relates to a process and apparatus for evaluating the print qualty of a printed product by means of a color measuring strip having individual measuring fields printed together with the printed product, and to the color measuring strip used in such process and apparatus.
One of the methods for evaluating print quality involves printing, together with the product, a color measuring strip constructed of a series of measuring fields of different types and colors, and then evaluating it colorimetrically. Densitometric measurement of the color measuring strips may be effected off-line by manual densitometers or by an automatic scanning densitometer, or on-line during operation of the printing machine by means of machine densitometers. Suitable scanning densitometers are described in U.S. patent application Ser. No. 363,538, filed Mar. 30, 1982, U.S. Pat. Nos. 3,995,958, and 4,289,405, among others, while examples of machine densitometers are found in U.S. Pat. Nos. 3,376,426 and 3,390,447, among others.
The scanning densitometer system described in U.S. Pat. No. 4,289,405 uses manually-applied markers in the determination of measuring positions of the measuring fields to be scanned. Aside from the fact that this system is not transferable to machine densitometers, information other than position information must be acquired by other, complicated means from the color measuring strips themselves, which in practice is difficult as well as expensive.